Hess' seafloor spreading hypothesis explains the process by which new oceanic crust is formed at mid-ocean ridges and then moves away from the ridge, gradually spreading apart. This movement of the oceanic crust is believed to be driven by convection currents in the mantle. The seafloor spreading hypothesis helped to provide evidence for the theory of plate tectonics, as it demonstrated how the movement of tectonic plates could be linked to the formation of new crust at mid-ocean ridges.
